The invention relates to a process for the separation of a phenol from a mixture obtained by carboxylation of the phenol.
When alkyl-substituted phenols are converted into alkyl salicylates, the yield is generally about 75%. When recycling of the starting alkyl-substituted phenols to the reactor is applied, the yield is increased to about 82%. Since the unreacted alkyl-substituted phenols and the desired alkyl salicylates product are difficult to separate in practice until now, the phenols have not been removed. In the production of overbased calcium salts of the above-mentioned alkylsalicylic acids, the phenols presence in the product may be tolerated for many applications. It would, however, be preferable if the alkyl-substituted phenols could be separated and used again as starting materials in the preparation of alkyl salicylates. In the overall reaction much higher yields of alkyl salicylates could be obtained, calculated on the alkyl phenols.
Applicant has now found that these phenols can be separated from said salicylates by the use of a certain membrane which selectively absorbs the phenols.